Explosive primer



Aug. 30, 1966 G. R. GAULD 3,269,315

EXPLOSIVE PRIMER Filed April 2. 1964 POWER SUPPLY INVENTOR. GODFREY R. GAULD ATTORNEYS.

United States Patent 3,269,315 EXPLOSIVE PRIMER Godfrey R. Gauld, Richmond, Ind., assignor to Avco Corporation, Richmond, Ind., a corporation of Delaware Filed Apr. 2, 1964, Ser. No. 356,710 3 Claims. (Cl. 102-701) The present invention relates to ordnance and comprises a novel electrical primer which not only transcends in utility the usual applications of electrical primers, but also possesses novel and unexpected advantages.

A primary object of the invention is to provide an explosive primer which comprises a semiconductor imbedded in an explosive charge, together with circuitry for driving the semiconductor into thermal runaway, thereby detonating the explosive charge in which it is imbedded.

Another object of the invention is to provide a primer in which the semiconductor functions in the multiple role of safety lock, power amplifier, and match for igniting an explosive mixture in a squib.

The invention is of particular utility in missile fuzing.

For a better understanding of the invention, together with other and further objects, advantages, and capabilities thereof, reference is made to the following description of the appended drawings, in which:

FIG. 1 is a block diagram of a primer in accordance with the invention; and

FIG. 2 is an axial longitudinal section through a projectile containing a burst charge and having installed therein a primer in accordance with the invention, this being one of many applications for which the invention is suitable.

The particular embodiment herein disclosed uses a three-element transistor in the primer, with low flash point high explosive powder 11 or paste surrounding it. A Type 2N263 transistor may be used successfully in some applications. Generally, high thermal resistance and low heat capacitance is desirable for high speed (i.e., short time) detonation a tion.

The three-lead element 10 may be housed in a shell similar to a .22 caliber cartridge. The external power requirements of the device are determined by the thermal and electrical characteristics of the semiconductor element 10. For a device using the 2N263 type transistor, the collector-emitter voltage would be about 40 volts for millisecond firing. It will depend entirely on the characteristics of the semiconductor element.

The base and emitter terminals 15 and 16 are connected together electrically prior to arming.

The emitter element of the transistor is indicated by the reference numeral 17, the base element by the reference numeral 18, and the collector element by the reference numeral 19. The power supply, connected between the emitter and the collector, is designated by the reference numeral 20.

The base may be biased beyond cut-off in some applications, which provides for safe handling of the primer. These connections might be broken by acceleration forces, for example, to arm the missile in flight. In accordance with the invention, firing is achieved by driving the semiconductor into thermal runaway by the application of a firing pulse between base-emitter terminals 15 and 16 of the semiconductor. For the Type 2N263, about .1 ampere is required. The resultant high collector-emitter current almost instantly raises the semiconductor temperature up to or above the flash point of the explosive charge 11 in which it is encased. Firing of the charge ensues.

The phenomenon of thermal runaway is per so well known, and is discussed in numerous authoritiesfor 3,269,315 Patented August 30, 1966 example, Handbook of Semiconductor Electronics, Hunter, section 13, paragraph 13.6, McGrawHill Book Company, New York, 1956; and Principles of Transistor Circuits, Shea, page 17, John Wiley & Sons, New York, 1953.

The firing pulse may be derived from an electronic distance-sensing system such as used in the proximity fuze, for example. Any arming sequence or source of the pulse command serves the purposes of this invention.

The prime objective achieved by this invention is the reduction in cost, volume, weight, and the danger in the testing of primers for explosive charges. The usual igniter and firing circuit is replaced by a more eflicient element. The semiconductor element 10 eliminates the need for and conserves the drive power usually dissipated in the firing circuit. In common firing devices only about half the power reaches the igniter heating element, the rest being lost in the associated circuitry.

Since the semiconductor element in this invention is basically a transistor or a silicon-controlled rectifier or a semiconductor diode, it can be safely tested for deterioration. In general the deterioration of semiconductor devices exhibits itself first as an increase in leakage current. Because the power required for testing leakage current is so minute, the active elment can be tested with no danger of igniting the primer.

The means and methods for installing primers in projectiles, missiles, and the like are well known. For example, making reference to vFIG. 2, the semiconductor in accordance with the invention is imbedded in a primer ignition charge 11, which in turn is surrounded by a conventional explosive mixture 21 disposed in conventional fashion within body 22 of a projectile 23 which includes the usual windshield 24.

The phenomenon of thermal runaway has heretofore been considered an undersirable attribute of semiconductors, and a condition to be guarded against. In accordance with the present invention this attribute is aflirmatively exploited to great advantage.

While there has been shown and described what is at present considered to be the preferred embodiment of the invention, it will be understood by those skilled in the art that various modifications and changes may be made therein without departing from the true scope of the invention as defined by the appended claims. The particular application herein shown and the parameters herein mentioned are presented by way of illustration and not of limitation.

I claim:

1. In ordnance, the combination of:

a three-element transistor type of semiconductor device having emitter, base, and collector electrodes, an ignition charge surrounding said device,

and means for driving the semiconductor device into thermal runaway.

2. The combination in accordance with claim 1, and a power supply connected between the emitter and collector electrodes.

3. The combination in accordance with claim 2, in which the means for driving the semiconductor device into thermal runaway comprises means for applying a pulse to the emitter-base circuit.

References Cited by the Examiner UNITED STATES PATENTS 3,211,096 10/1965 Forney et al. l0270.2 X

BENJAMIN A. BORCHELT, Primary Examiner.

W. C. ROCH, Assistant Examiner. 

1. IN ORDNANCE, THE COMBINATION OF: A THREE-ELEMENT TRANSISTOR TYPE OF SEMICONDUCTOR DEVICE HAVING EMITTER, BASE, AND COLLECTOR ELECTRODES, AN IGNITION CHARGE SURROUNDING SAID DEVICE, AND MEANS FOR DRIVING THE SEMICONDUCTOR DEVICE INTO THERMAL RUNAWAY. 